Blink for Mobile is a VoIP client for SIP2SIP.info with which you can make audio and video calls as well as group video calls.
To use Blink for Mobile you need a SIP2SIP account, if you don't have one you can create it from within the application.
You can call and receive calls to and from any publicly routable SIP address in the world, not just sip2sip.info domain. Supported codecs are Opus and G.711 for audio and H.264 and VP8 for video.
Known limitations and features that will be addressed in future versions:
* No incoming calls while in the background